问答详情
源自：9-3 getElementsByTagName()方法

为什么第一个函数的调用里不能用getElementsByTagName呢

<!DOCTYPE HTML>
<html>  
<head>  
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />  
<title>JavaScript</title>  
</head>  
<body>  
    
        <form name="Input">
            <table align="center" width="500px" height="50%" border="1">
                <tr>
                    <td align="center" width="100px">
                        学号:
                    </td>
                    <td align="center" width="300px">
                        <input type="text" id=userid name="user" onblur="validate();">
                        <div id=usermsg></div>
                    </td>
                </tr>
                <tr>
                    <td align="center" width="100px">
                        姓名:
                    </td>
                        <td align="center">
                        <input type="text" name="name">
                    </td>
                </tr>
                <tr>
                    <td align="center" width="%45">
                        性别:
                    </td>
                    <td align="center">
                        <input type="radio" name="sex" value="男">
                        男
                        <input type="radio" name="sex" value="女">
                        女
                    </td>
                </tr>
                <tr>
                    <td align="center" width="30%">
                        年龄:
                    </td>
                    <td align="center" width="300px">
                        <input type="text" name="age">
                    </td>
                </tr>
                <tr>
                    <td align="center" width="100px">
                        地址:
                    </td>
                    <td align="center" width="300px">
                        <input type="text" name="addr">
                    </td>
                </tr>

            </table>
        </form>
        <h1 id="myHead" onclick="getValue()">
            看看三种获取节点的方法?
        </h1>
        <p>
            点击标题弹出它的值。
        </p>
        <input type="button" onclick="getElements()"
            value="看看name为sex的节点有几个?" />
        <Br>
        <input type="button" onclick="getTagElements()"
            value="看看标签名为input的节点有几个?" />
            
     <script type="text/javascript">
         function getValue()
          {
              var myH=document.getElementsByTagName("myHead");
              alert(myH.innerHTML)
          }
          function getElements()
          {
             var myS = document.getElementsByName("sex");
              alert(myS.length);
          }

          function getTagElements()
          {
              var myI = document.getElementsByTagName("input");
              alert(myI.length);
          }
         
     </script>        

    </body>
</html>


提问者：doits 2016-05-14 01:36

个回答

  • 慕娘4859975
    2016-07-30 01:52:23

    function getValue()
          {
              var myH=document.getElementsByTagName("h1");
              alert(myH[0].innerHTML)
          }


    1
  • Sunnylincon
    2016-05-28 22:41:30

    alert(myH.innerHTML),innerHTML 在这里用于获取myH 的内容

    getElementsByTagName()是返回带有指定标签名的节点对象的集合，myHead并不是标签，你可以试一下，

    var myH=document.getElementsByTagName("myHead");

    alert(myH.length)；弹出的框是0（数组长度为0），也就是说计算机一个myHead都没有收到，于是alert(myH.innerHTML)；时，myH本身并没有什么内容，应该会输出undefined



    1
  • 违丶心
    2016-05-15 17:36:58

    你这里的"myHead"是一个id,不能用getElementsByTagName()方法的

    0
  • 卡布奇诺0929
    2016-05-14 09:56:33

    var myH=document.getElementsByTagName("myHead");  

    getElementsByTagName("TagName")标签名称   应写为

    var myH=document.getElementsByTagName("H1");

    0